In Campylobacter jejuni the sugar 2,4-diacetamido-2,4,6-trideoxy-α-D-glucopyranose, termed N,N ′-diacetylbacillosamine (Bac2,4diNAc), is the first carbohydrate in the glycoprotein N-linked heptasaccharide. Starting with uridine diphosphate-N-acetylglucosamine (UDP-GlcNAc) two enzymes of the general protein glycosylation (Pgl) pathway in C. jejuni (PglF and PglE) have been recently shown to modify this sugar nucleotide to form UDP-2-acetamido-4-amino-2,4,6-trideoxy-α-D-glycopyranose (UDP-4-amino-sugar) [Schoenhofen, I. C., et al. (2006) J Biol Chem 281, 723-732]. PglD has been proposed to catalyze the final step in N,N′-diacetylbacillosamine synthesis by N-acetylation of the UDP-4-amino-sugar at the C4 position. We have cloned, overexpressed and purified PglD from the pgl locus of C. jejuni NCTC 11168 and identified it as the acetyltransferase that modifies the UDP-4-amino-sugar to form UDP-N,N′-diacetylbacillosamine, utilizing acetyl coenzyme A as the acetyl group donor. The UDP-N,N′-diacetylbacillosamine product was purified from the reaction by reverse phase C18 HPLC and the structure determined by NMR analysis. Additionally, the full-length PglF was overexpressed and purified in the presence of detergent as a GST-fusion protein allowing for derivation of kinetic parameters. We found that the UDP-4-aminosugar was readily synthesized from UDP-GlcNAc in a coupled reaction using PglF and PglE. We also demonstrate the in vitro biosynthesis of the complete heptasaccharide lipid-linked donor by coupling the action of eight enzymes (PglF, PglE, PglD, PglC, PglA, PglJ, PglH, and PglI) in the Pgl pathway in a single reaction vessel.Campylobacter jejuni is the Gram-negative enteropathogen identified as the primary cause of gastroenteritis in humans and the most frequent infection to precede the peripheral neuropathy Guillain-Barré syndrome (1-3). Infection of humans generally occurs by ingestion of contaminated livestock or water. Although the mechanism of infection is not clearly understood, production of glycolipids and glycoproteins by the pathogen have been found to influence cell motility, host-cell interactions, and competence for DNA uptake (4-6). As resistance to antimicrobial agents rises, the potential for development of novel therapeutics against enzymes that produce glycoconjugates has intensified efforts targeted at the characterization of their biosynthetic pathways. In C. jejuni four major glycan structures have been identified: lipooligosaccharide (LOS), capsule, O-linked glycan, and N-linked glycan *To whom correspondence should be addressed: Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139. E-mail: imper@mit.edu, (v) 617-253-1838, (f)
NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript (7)(8)(9)(10). The genes coding for enzymes that synthesize these glycan moieties have been found in clusters throughout the C. jejuni genome. The respective biochemical functions of the gene products have been assigned on the b...